Free piston-type pump

ABSTRACT

A free piston-type pump having two or more cylinders with each cylinder being connected to a chamber and a free piston being reciprocatingly received therein. Each chamber is connected to a common inlet and outlet manifold. A fluid to be pumped is connected to the inlet manifold by a pump which provides a low positive pressure therein, while a high-pressure power fluid is connected to an opposite side of the piston so as to reciprocate the piston with great force in one direction while the fluid to be pumped reciprocates the piston with a lesser force in an opposite direction. Hydraulic flow control means connected to a plurality of such cylinders provides uninterrupted use of the power fluid by continuously downstroking one piston while another piston is on the upstroke.

United States Patent 7 2| inventor Archie W. Beemnn Box 245, Odessa, Tex. 79760 [21] Appl. No. 885,843 [22] Filed Dec. 17,1969 [45] Patented Nov. 9, I971 (54] FREE PISTON-TYPE PUMP 10 Claims, 6 Drawing Figs.

[52] US. Cl 417/390, 417/568, 417/392 [51] Int. Cl F04b 9/08, F04b 21/02, F0411 17/00 [50] Field ofSearch 417/56 205, 271, 248, 225, 342, 390, 392, 393; 184/29; 222/249, 334

[56] Relerenees Cited UNITED STATES PATENTS 801,612 10/1905 Schramm 4l7/392X 1,991,595 2/1935 Creveling 3,185,098 5/1965 Lundh In'mary bliuminrr-Rohcrt M, Walker Attorney-Marcus 1.. Bates ABSTRACT: A free pislon-type pump having two or more cylinders with each cylinder heing connected to a chamber and a free piston being reciprocatingly received therein. Each chamber is connected to a common inlet and outlet manifold. A fluid to be pumped is connected to the inlet manifold by a pump which provides a low positive pressure therein. while a high-pressure power fluid is connected to an opposite side of the piston so as to reciprocate the piston with great force in one direction while the fluid to be pumped reciprocates the piston with a lesser force in an opposite direction. Hydraulic flow control means connected to a plurality of such cylinders provides uninterrupted use of the power fluid by continuously downstroking one piston while another piston is on the upstroke.

PAIENTEnuuv e lsm INVILNI ()R. Archie WBeeman 7 Marcus LBafes FREE PISTON-TYPE PUMP BACKGROUND OF THE INVENTION Highpressure fluid pumps for moving abrasive liquids or slurries, such as drilling mud for example, are known to those skilled in the art. A mud pump of the prior art is usually a massive apparatus having several cylinders within which there is slidably received a piston. The piston is connected to a large connecting rod which in turn is journaled to a crank for imparting reciprocatory motion thereinto. The mud pump cylinders are usually in the form of counterbores which are formed from a solid casting weighing thousands of pounds. The abrasive nature of the pumped liquid causes the piston to rapidly wear the cylinders, and after a short life the cylinders must be relined. Relining the cylinders is expensive because it is usually necessary to disassemble the heavy pump and accordingly all of this repair and maintenance must be undertaken in a well-equipped machine shop. It is desirable to be able to replace the rapidly wearing components of a mud pump in an improved, economical, and efficient manner. It is furthermore desirable to be able to efl'ect such a replacement and repair in the field. It is also desirable to be able to reduce the tremendous weight of a mud pump while at the same time sacrificing none of its strength and ruggedness. It is also desirable to reduce the cost of a mud pump as well as improving its operation, especially from the viewpoint of eliminating the multiplicity of moving parts generally associated therewith. It would be even more desirable to provide a mud pump which is lighter, more efficient, less expensive, and more easily repaired than the mud pumps represented by the prior art.

SUMMARY OF THE INVENTION The present invention comprehends a pump assembly for pumping one fluid with another fluid by utilizing a plurality of pumps, each having an elongated cylinder connected to a case, and with a high-pressure hydraulic pump and control system applying a power fluid for reciprocating a free piston within each of the cylinders thereof, while the fluid being pumped upstrokes the piston. The control system advantageously permits movement of the pistons in a manner which continuously uses the power provided by the high-pressure pump. The cylinders admit employment of an extremely long piston stroke and are assembled to the pump in a manner to enable rapid field replacement thereof.

It is therefore an object of the present invention to provide a pump assembly for pumping one fluid with another fluid.

Another object of the present invention is the provision of a pump assembly having a minimum of moving parts associated therewith.

Another object of the present invention is the provision of an improved pump assembly which uses a power fluid in order to actuate a free piston in a manner to cause fluid to flow under high pressure.

Still another object of the present invention is the provision of a hydraulic pumping system associated with a plurality of pumps wherein the pumps jointly cooperate to continuously utilize the work delivered by the hydraulic system.

A still further object of the present invention is the provision of an improved pump assembly for pumping one fluid with another fluid wherein the cylinder and piston of the pump can be rapidly replaced by ordinary workmen in the oil field.

The above objects are attained in accordance with the present invention by the provision of a pump assembly which is fabricated essentially as outlined in the above abstract and summary.

Other objects and advantages of this invention will become readily apparent to those skilled in the art upon reading the following detailed description and claims and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical cross-sectional view of a pump assembly made in accordance with the present invention, with some parts thereof being shown unsectioned, and with other parts being included in order to better illustrate the details thereof;

FIG. 2 is a partly diagrammatical, partly schematical representation of one form of the present invention, and showing a top plan view of the pump assembly disclosed in FIG. I;

FIG. 3 is a fragmentary, partly diagrammatical side elevational view of the pump disclosed in FIGS. 1 and 2;

FIGS. 4 and 5 are each enlarged crosssectional views taken along lines 4-4 and 5-5, respectively, of FIG. I; and

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 1 and showing a part of the pump assembly seen in the foregoing figures.

DETAILED DESCRIFT ION OF THE PREFERRED EMBODIMENT FIG. 1 is a vertical cross-sectional view of a pump assembly which pumps one fluid, such as drilling mud, by utilizing another fluid, such as hydraulic oil, for the pumping power. A pump case 12 has removably attached thereto an inlet manifold 14 having an internal bore 15 which forms a common inlet chamber for receiving fluid therein. A check valve 16 permits fluid to flow from the inlet chamber towards an outlet or high-pressure manifold 18. The high-pressure manifold has an internal bore 19 which forms a common outlet chamber, and is provided with a check valve 20, similar or identical to the inlet check valve.

Vertically upstanding barrel or cylinder 22 is spaced apart from an identical cylinder 24 so as to provide a plurality of working barrels, as will be more fully discussed later on. The lower extremity of each cylinder is provided with a flange 26 which enables the cylinder to be rigidly but removably affixed to an upper surface 28 of the case by the illustrated fastener means.

The cylinder is provided with the usual internal constant diameter bore 30, and is further provided with a closure means 32 which for purposes of illustration, is shown as an ordinary threaded cap 32 having a centrally located aperture for receiving a coupling means 34 so as to enable power fluid attachments to be removably attached thereto.

Reciprocatingly received in sealed relationship with respect to the inside peripheral wall surface of the cylinder there is illustrated a free piston assembly comprised of a centrally disposed piston mandrel having enlargement 36 located intermediate opposed end portions 38, 39. Retainer means 40, 41 are removably affixed to the marginal end portions of the mandrel and maintain the free piston components in assem: bled condition by compressing the circumferentially disposed seal means 42 and its complementary expander means 44, along with the seal 42' and the expander 46 towards the enlargement. The opposite retainer means likewise compresses the seals 43, 43' along with the complementary expanders 48, 50 towards the enlargement of the mandrel so as to maintain the seals properly positioned along the longitudinally extending mandrel.

Shoulder 52 provides a stop means against which the lower retainer means is abuttingly received at the extreme lower end of travel of the downward or power stroke. ()-rings 54 circumferentially extend about and provide a high-pressure seal at the lower terminal end of the cylinder. The cylinder communicates with the illustrated pump case cavity 58 by means of piston-working passageway 56.

The pump case can be provided with any number of cavities S8, 58' with a cylinder being arranged in communication with each of the cavities in the illustrated manner of FIGS. 1, 3, and 6.

Each cavity is provided with a circumferentially extending seat 62 which receives the before mentioned check valve therein with the common manifold I8 having a complementary shoulder formed thereon which engages a face of each check valve means, as seen in FIG. 1 in conjunction with FIG. 3. Shoulder 64 receives the inlet check valve in a similar manner, with the common inlet chamber communicating with one side of each inlet check valve.

Looking now in greater detail to FIG. 2, the inlet manifold is seen to have a conduit 70 connected to a low-pressure highvolume pump means 71 which in turn is connected to the indicated source of fluid which is to be pumped. High-pressure outlet manifold 18 is connected to an outlet means in the form of a high-pressure outlet conduit 72, which, in the case of drilling mud, would be flow-connected to the swivel of a drilling rig (not shown).

The power fluid is connected to the upper cylinder chamber of each cylinder of the pump assembly by the illustrated coupling 34, for example, and controller 77' is connected or arranged in a manner to sense the pressure of the power fluid contained within the upper portion of the cylinder. Three-way motor valves 77, 78 control the flow of high-pressure fluid between hydraulic pump 81, the illustrated reservoir, and each of the upper cylinder chambers by means of the illustrated flow conduits 79, 80, 82. Controllers 77', 78' permit high pressure fluid to alternately flow through one of the valves 77, 78 until the end of one of the piston strokes, whereupon an increase in pressure sensed by the controller shifts the fluid from one upper cylinder chamber to another, and at the same time connects the reservoir to the upper cylinder chamber which has completed its stroke.

In assembling the apparatus of the present invention, each cavity 58, 58' is provided with a check valve at the inlet and outlet side of the cavity, and the manifolds are each attached to the pump case by any suitable fastener means (not shown) so as to force the valve side of each manifold towards the case, thereby effecting a high-pressure seal between the case, valves, and manifold. The inlet manifold has a common chamber which is in communication with each of the inlet check valves. Similarly, the common outlet chamber of the outlet manifold is in communication with each of the outlet check valves which in turn communicates with each cavity of the case. Accordingly, a low-pressure high-volume pump 71 attached to an inlet chamber can be arranged to cause mud to flow through the inlet manifold and inlet check valve, and into each of the cavities.

As the power fluid alternately drives the pistons within the various cylinders in a downward direction, mud which has previously flowed into each of the lower cylinder chambers will now be displaced from the cylinder by the free piston, and the flow of mud from the lower cylinder chamber back into the cavity will move the inlet check valve to the closed position while the outlet check valve will open and permit the mud to flow into the outlet manifold with the pressure thereof being proportional to the pressure of the power fluid effected by pump 81.

As a piston completes its downward stroke, and preferably before retainer 40 abuts shoulder 52, controller 77 shifts control valve 77 so as to connect the upper cylinder chamber to the reservoir whereupon fluid will cease to be displaced from the lower cylinder, causing the outlet check valve to close and the piston to be forced into the upper cylinder chamber because of the action of the low pressure mud pump 71. The piston will continue to upstroke until the valve 77 is again shifted, or until the upper retainer 41 abuts the cap 32. It is pointed out that the pump pressure at the inlet manifold is of a sufficient value to displace the power fluid from the upper cylinder chamber as the free piston upstrokes within the cylinder.

As hydraulic fluid is displaced from the upper cylinder chamber, it flows back through the three-way valve 77, through conduit 79, and into the reservoir. During this time controller 78 has moved three-way valve 78' to flow position which enables power fluid to flow from the high-pressure hydraulic pump 81, along conduit 82, through valve 78, conduit 76, and into an adjacent upper cylinder chamber 24, thereby driving its piston in a downward direction. As the piston within cylinder 24 reaches its bottommost stroke, valve 78,is shifted to allow fluid to flow from the upper cylinder chamber, back to the reservoir. The controllers 77', 78' are interconnected or synchronized with respect to each other 5 whereby one piston is always on a downstroke to thereby continually utilize the power fluid from the hydraulic pump.

Should a piston stroke to its extreme lower limit, the illustrated retainer means will abut shoulder 52, for example, thereby increasing the pressure in the upper cylinder chamber, whereupon the controller immediately shifts the power fluid flow to another upper cylinder chamber while at the same time connecting the first upper cylinder chamber back to the reservoir.

It is preferred to connect the cylinder in an upstanding vertical position as illustrated in F IG. 1 so as to prevent accumulation of debris within the lower cylinder chamber; however, where the cylinders exceed 8 feet in length, it is preferred to arrange them horizontally. While two cylinders have been shown in the preferred embodiment, it should be understood that still additional cylinders can be incorporated if deemed desirable.

I claim:

1. A pump assembly for pumping one fluid with a power fluid comprising; in combination:

a pump case, said pump case having means forming a cavity therein, inlet and outlet check valve means for controlling flow of the one fluid into and out of the cavity;

an elongated cylinder means attached to said case and having an internal bore which is in flow communication with the cavity;

a free piston means reciprocatingly received within the internal bore and dividing the internal bore of said cylinder into upper and lower cylinder chambers;

said free piston including a mandrel having opposed ends with an enlargement formed thereon intermediate the opposed ends, and a retainer means removably received at each opposed end;

an expander and a seal means compressed between each said retainer and said enlargement with said expander urging said seal means against the inside peripheral wall surface of the internal bore;

an inlet manifold flow connected to said inlet check valve; means including a low-pressure pump flow connected to said inlet manifold for causing the one fluid to flow through said inlet manifold and into the cavity to thereby upstroke said piston;

an outlet manifold flow connected to said outlet check valve for conducting high-pressure fluid flow therefrom;

a source of power fluid for downstroking said piston; flow control means flow connecting the source of power fluid to said upper cylinder chamber; said flow control means providing cyclic flow of power fluid from the source to said upper cylinder chamber, and vice versa, to thereby downstroke said free piston and then to enable the power fluid to be exhausted from the upper chamber upon said free piston being upstroked.

60 2. The pump assembly of claim 1, wherein said pump case includes means forming a second cavity therein, inlet and outlet check valve means for controlling flow of the one fluid through said second cavity;

a second elongated cylinder having means forming an internal bore; said bore being in communication with said second cavity; said second cylinder being attached to and depending from said case;

a second free piston reciprocatingly received within the internal bore and dividing said second cylinder into upper and lower cylinder chambers;

said inlet manifold being flow connected to said inlet check valve of each pump; pump means for forcing a low-pressure flow of the one fluid through said inlet manifold and into the second cavity for upstroking said second free 7 5 piston;

said outlet manifold being connected to said outlet check valve of said second cavity for conducting high-pressure fluid flow therefrom;

said flow control means connecting the source of power fluid to said upper cylinder chamber of the second cylinder, said flow control means providing cyclic flow of fluid from the source to said upper chamber of said second cylinder, and vice versa, to thereby downstroke said second free piston and to enable the power fluid to be exhausted from the upper chamber upon said second free piston being upstroked; whereby:

said flow control means provides power fluid flow to the first recited cylinder while spent power fluid is being returned from the second cylinder.

3. The pump assembly of claim 1 wherein said means for conducting flow of one fluid into said inlet cavity includes a pump means having an output pressure which exceeds the static pressure of the upper cylinder chamber when the piston is upstroking.

4. The pump assembly of claim 1, wherein said pump case includes at least two cavities, with each cavity having a cylinder assembly attached thereto;

said flow control means provides flow of power fluid to one upper cylinder chamber while spent power fluid returns from another upper cylinder chamber;

said means for conducting flow of one fluid into said inlet cavity includes a pump means having a pressure output which exceeds the static pressure of the upper cylinder chamber when the piston therein is upstroking.

,5. The pump assembly of claim 4 wherein said flow control means further includes a hydraulic pump, a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to a second upper cylinder chamber and to said reservoir;

pressure responsive means connected to cause said first and second valve means to bypass fluid flow from an upper cylinder chamber when the free piston reaches the end of its stroke.

6. The pump assembly of claim 1 wherein said pump case includes at least two cavities, with each cavity having a cylinder attached thereto;

said flow control means provides flow of power fluid to one upper cylinder chamber while spent power fluid returns from another upper cylinder chamber;

said flow control means further includes a hydraulic pump,

a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to a second upper cylinder chamber and to said reservoir;

pressure responsive means connected to cause said valve means to bypass power fluid flow from a chamber when the free piston thereof reaches the end of its stroke.

7. A pump assembly for pumping one fluid with a power fluid comprising; in combination:

a pump case, said pump case having means forming two separate cavities therein, inlet and outlet check valve means for controlling flow of the one fluid through each of the cavities;

an elongated cylinder means for each of said cavities, each cylinder having an internal bore, means by which said internal bore is in flow communication with its respective said cavity;

a free piston means for each cylinder, each piston being reciprocatingly received within the internal bore and dividing the cylinder within which it is located into upper and lower cylinder chambers;

an inlet manifold, means by which said inlet manifold is flow connected to each of said inlet check valves, a low-pressure pump means for causing flow of the one fluid through said inlet manifold and into each of the cavities for upstroking each said piston;

an outlet manifold, means by which said outlet manifold is flow connected to each of said outlet check valves for conducting highressure fluid flow from the pum a source of power uid for downstroking each said piston;

flow control means connecting the source of power fluid to each said upper cylinder chambers, said flow control means providing cyclic flow of fluid from the source to alternate ones of said upper cylinder chambers, and vice versa, to thereby downstroke one said free piston and thereafter to enable the power fluid to be exhausted from the upper chamber upon said free piston being upstroked.

8. The pump assembly of claim 7 wherein said free piston includes:

a mandrel having opposed ends with an enlargement formed thereon intermediate the opposed ends, and a retainer removably received at each opposed end;

an expander and a seal means compressed between each said retainer and said enlargement with said expander urging said seal means against the peripheral wall surface of the internal bore.

9. The pump assembly of claim 7, wherein said flow control means provides flow to one upper cylinder chamber while fluid returns from another upper cylinder chamber;

said low-pressure pump means for conducting flow of one fluid into said inlet cavity includes a pump having a pressure output which exceeds the static pressure of the upper cylinder chamber when the piston therein is upstrokingv 10. The pump assembly of claim 7 wherein said flow control means further includes a hydraulic pump, a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to said second upper cylinder chamber and to said reservoir;

pressure responsive means connected to each cylinder chamber for causing said valve means to preclude fluid flow into the upper chamber when the free piston reaches the end of its downstroke. 

1. A pump assembly for pumping one fluid with a power fluid comprising; in combination: a pump case, said pump case having means forming a cavity therein, inlet and outlet check valve means for controlling flow of the one fluid into and out of the cavity; an elongated cylinder means attached to said case and having an internal bore which is in flow communication with the cavity; a free piston means reciprocatingly received within the internal bore and dividing the internal bore of said cylinder into upper and lower cylinder chambers; said free piston including a mandrel having opposed ends with an enlargement formed thereon intermediate the opposed ends, and a retainer means removably received at each opposed end; an expander and a seal means compressed between each said retainer and said enlargement with said expander urging said seal means against the inside peripheral wall surface of the internal bore; an inlet manifold flow connected to said inlet check valve; means including a low-pressure pump flow connected to said inlet manifold for causing the one fluid to flow through said inlet manifold and into the cavity to thereby upstroke said piston; an outlet manifold flow connected to said outlet check valve for conducting high-pressure fluid flow therefrom; a source of power fluid for downstroking said piston; flow control means flow connecting the source of power fluid to said upper cylinder chamber; said flow control means providing cyclic flow of power fluid from the source to said upper cylinder chamber, and vice versa, to thereby downstroke said free piston and then to enable the power fluid to be exhausted From the upper chamber upon said free piston being upstroked.
 2. The pump assembly of claim 1, wherein said pump case includes means forming a second cavity therein, inlet and outlet check valve means for controlling flow of the one fluid through said second cavity; a second elongated cylinder having means forming an internal bore; said bore being in communication with said second cavity; said second cylinder being attached to and depending from said case; a second free piston reciprocatingly received within the internal bore and dividing said second cylinder into upper and lower cylinder chambers; said inlet manifold being flow connected to said inlet check valve of each pump; pump means for forcing a low-pressure flow of the one fluid through said inlet manifold and into the second cavity for upstroking said second free piston; said outlet manifold being connected to said outlet check valve of said second cavity for conducting high-pressure fluid flow therefrom; said flow control means connecting the source of power fluid to said upper cylinder chamber of the second cylinder, said flow control means providing cyclic flow of fluid from the source to said upper chamber of said second cylinder, and vice versa, to thereby downstroke said second free piston and to enable the power fluid to be exhausted from the upper chamber upon said second free piston being upstroked; whereby: said flow control means provides power fluid flow to the first recited cylinder while spent power fluid is being returned from the second cylinder.
 3. The pump assembly of claim 1 wherein said means for conducting flow of one fluid into said inlet cavity includes a pump means having an output pressure which exceeds the static pressure of the upper cylinder chamber when the piston is upstroking.
 4. The pump assembly of claim 1, wherein said pump case includes at least two cavities, with each cavity having a cylinder assembly attached thereto; said flow control means provides flow of power fluid to one upper cylinder chamber while spent power fluid returns from another upper cylinder chamber; said means for conducting flow of one fluid into said inlet cavity includes a pump means having a pressure output which exceeds the static pressure of the upper cylinder chamber when the piston therein is upstroking.
 5. The pump assembly of claim 4 wherein said flow control means further includes a hydraulic pump, a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to a second upper cylinder chamber and to said reservoir; pressure responsive means connected to cause said first and second valve means to bypass fluid flow from an upper cylinder chamber when the free piston reaches the end of its stroke.
 6. The pump assembly of claim 1 wherein said pump case includes at least two cavities, with each cavity having a cylinder attached thereto; said flow control means provides flow of power fluid to one upper cylinder chamber while spent power fluid returns from another upper cylinder chamber; said flow control means further includes a hydraulic pump, a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to a second upper cylinder chamber and to said reservoir; pressure responsive means connected to cause said valve means to bypass power fluid flow from a chamber when the free piston thereof reaches the end of its stroke.
 7. A pump assembly for pumping one fluid with a power fluid comprising; in combination: a pump case, said pump case having means forming two separate cavities therein, inlet and outlet check valve means for controlling flow of the one fluid through each of the cavities; an elongated cylinder means for each of said cavities, each cylinder having an internal bore, means by which said internal bore is in flow communication with its respective said cavity; a free piston means for each cylinder, eaCh piston being reciprocatingly received within the internal bore and dividing the cylinder within which it is located into upper and lower cylinder chambers; an inlet manifold, means by which said inlet manifold is flow connected to each of said inlet check valves, a low-pressure pump means for causing flow of the one fluid through said inlet manifold and into each of the cavities for upstroking each said piston; an outlet manifold, means by which said outlet manifold is flow connected to each of said outlet check valves for conducting high-pressure fluid flow from the pump; a source of power fluid for downstroking each said piston; flow control means connecting the source of power fluid to each said upper cylinder chambers, said flow control means providing cyclic flow of fluid from the source to alternate ones of said upper cylinder chambers, and vice versa, to thereby downstroke one said free piston and thereafter to enable the power fluid to be exhausted from the upper chamber upon said free piston being upstroked.
 8. The pump assembly of claim 7 wherein said free piston includes: a mandrel having opposed ends with an enlargement formed thereon intermediate the opposed ends, and a retainer removably received at each opposed end; an expander and a seal means compressed between each said retainer and said enlargement with said expander urging said seal means against the peripheral wall surface of the internal bore.
 9. The pump assembly of claim 7, wherein said flow control means provides flow to one upper cylinder chamber while fluid returns from another upper cylinder chamber; said low-pressure pump means for conducting flow of one fluid into said inlet cavity includes a pump having a pressure output which exceeds the static pressure of the upper cylinder chamber when the piston therein is upstroking.
 10. The pump assembly of claim 7 wherein said flow control means further includes a hydraulic pump, a first valve means connected to the upper cylinder chamber and to a reservoir, a second valve means connected to said second upper cylinder chamber and to said reservoir; pressure responsive means connected to each cylinder chamber for causing said valve means to preclude fluid flow into the upper chamber when the free piston reaches the end of its downstroke. 